import math


def main():
    x1, y1, x2, y2 = map(float, input().split())

    ans = math.sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2)
    print(ans)

if __name__ == "__main__":
    main() import math math def main():
    x1, y1, x2, y2 = map(float, input().split())

    ans = math.sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2)
    print(ans) main x1, y1, x2, y2 = map(float, input().split()) x1 map(float, input().split()) map float input().split() ().split () input split y1 x2 y2 ans = math.sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2) ans math.sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2) math.sqrt math sqrt (x1 - x2) ** 2 + (y1 - y2) ** 2 (x1 - x2) ** 2 x1 - x2 x1 x2 2 (y1 - y2) ** 2 y1 - y2 y1 y2 2 print(ans) print ans if __name__ == "__main__":
    main() __name__ == "__main__" __name__ "__main__" main() main def main():
    x1, y1, x2, y2 = map(float, input().split())

    ans = math.sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2)
    print(ans) def main():
    x1, y1, x2, y2 = map(float, input().split())

    ans = math.sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2)
    print(ans) main
import math


def main():
    x1, y1, x2, y2 = map(float, input().split())

    ans = math.sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2)
    print(ans)

if __name__ == "__main__":
    main()